A typical optical coupler comprises several separate lens and mirror elements, which are mounted in specified locations on a structure called an optical table, and which have configurations and orientations with respect to each other that are precisely specified so that an optical signal entering the optical coupler from a source can be transmitted therethrough to a receiving device without significant distortion.
In an application in which a typical optical coupler is subjected to extreme temperature fluctuations (e.g., an extraterrestrial space application), thermal expansions and contractions of the optical table--and of the separate lens and mirror elements mounted thereon--can occur due to the temperature fluctuations. Such thermal expansions and contractions tend to produce changes in focal positions of the lens and mirror elements, and thereby to introduce significant distortions into optical signals being transmitted through the optical coupler. Such changes in the focal positions of the lens and mirror elements adversely affect the efficiency with which optical signals can be transmitted through optical coupler.
A need has been perceived in the prior art for an optical coupler that is substantially unaffected by extreme temperature fluctuations.